    Patent Document 1: JP-A-H04-214736    Patent Document 2: JP-A-2005-60281    Patent Document 3: JP-A-2007-50340
In general, a reactor for use in obtaining a new substance by the chemical reaction between two or more reactants or the same reactants is broadly divided into a batch type reactor and a flow (continuous) type reactor. In the case of a batch type reactor, a solvent, a substrate, and a reactant are placed in a reactor typified by a flask used in a laboratory, and are then stirred by, for example, a stirrer to perform a reaction. On the other hand, in the case of a flow type reactor such as an apparatus disclosed in Patent Document 1, a substrate solution is stirred and mixed and then flowed, and a reactant is added to the flowed substrate solution under stirring to perform a reaction. Both the batch type reactor and the flow type reactor are practically used in industry, and their reaction fields, of course, have a capacity. The capacity of such a reactor has an influence on nonuniformity in its reaction field. For example, in a case where a reactant is added to a uniform substrate solution to perform a chemical reaction, a certain period of time is required to make the concentration of the reactant uniform. The same can be said for temperature as a reaction condition. More specifically, in a case where a reactor is externally or internally heated or cooled, a certain period of time is required to heat or cool the entire reactor to a certain temperature. Further, it can be considered that it is very difficult to make the temperature of the entire reaction field in the reactor completely uniform. Further, in a case where a reactant is added in order to a solvent and a substrate placed in a batch type reactor, reaction conditions at the end of adding the reactant are already different from those at the start of adding the reactant. Nonuniformity of reaction conditions in a reaction field caused by the above-described factors has an influence on a finally-obtained reaction product. That is, reaction conditions vary even in the same reactor, and therefore a target reaction cannot be performed ideally. For example, a main reaction and a side reaction cannot be completely selectively performed and this results in the generation of a by-product, and in the case of polymerization reaction, it is difficult to obtain a reaction product having a uniform molecular weight distribution. Further, when adhesion to the inner wall of a reactor is taken into consideration, the yield of a reaction product is naturally lowered. In order to solve such problems related to a reaction field, a dynamic stirring device such as a stirrer or a turbine or a static stirring device such as a jet mixer is usually provided in a reactor. In this case, the speed of mixing a subject reaction mixture fluid is increased by such a stirring device for the purpose of achieving uniformity in a reaction field at a speed comparable to a reaction speed. However, nonuniformity in the reaction field again becomes a problem as the viscosity of the reaction mixture fluid increases. Even when the viscosity of the reaction mixture fluid is increased, stirring is continued for the purpose of instantaneously achieving uniformity in the reaction field so that power required for stirring naturally keeps steadily increasing. Further, there is also a problem that when the reaction fluid is heated in a short period of time, excessive heat energy is required due to a large temperature gradient.
The above-described problems are likely to become particularly serious in chemical reactions using organic compounds as starting materials, typified by Friedel-Crafts reaction, nitration reaction, addition reaction, elimination reaction, transfer reaction, polycondensation, coupling reaction, acylation, carbonylation, aldehyde synthesis, peptide synthesis, aldol reaction, and indole reaction, that is, in reactions, such as organic reactions, where a side reaction proceeds under reaction conditions very similar to those of a main reaction, or in reactions that need to form a reaction intermediate, or in reactions performed to obtain an intermediate. These reactions are required to make reaction conditions such as a concentration gradient and a temperature gradient uniform throughout a reaction field.
Further, the above-described organic reactions involve safety issues and dangers in spite of the fact that they are frequently used in chemical industry. In most cases, relatively large amounts of highly toxic chemical substances are used, which poses significant risks to humans and the environment, and solvents are environmental pollutants from various viewpoints, which creates particular problems. Further, in a case where, for example, carbon disulfide is used as a starting material, its low vapor pressure and flash point indicate that there is an additional risk that an explosible air/carbon disulfide mixture will be produced. Further, in the case of Friedel-Crafts acylation, there is a risk posed by its highly exothermic reaction, and in the case of nitration, there is also a serious risk of explosion in addition to a risk posed by its exothermic reaction. These risks come to the fore along with scale-up for real production.
In order to solve the above problems, a micromixer or a microreactor is proposed in, for example, Patent Documents 2 and 3, and it is advantageous in that a target substance can be synthesized in a very small amount, temperature control can be highly efficiently performed, interface reaction can be highly efficiently performed, and mixing is efficiently performed. However, when the general microreactor is used, there are many advantages in the micro-device and system, but as the micro-flow path diameter is decreased, pressure loss is inversely proportional to the biquadrate of the flow path; that is, an extremely high feeding pressure becomes necessary thus making a pump for actually feeding a fluid hardly available. In addition, there are many problems; for example, a phenomena of clogging of a flow path with a product occurs when the reaction is accompanied by separation, a micro-flow path is clogged with bubbles generated by a reaction, a microscopic space is not effective or applicable to every reaction although the speed of molecular diffusion is fundamentally expected for the reaction. Actually, the reaction should be attempted by trial and error in order to select good results. In the case of a microreactor disclosed in Patent Document 2, the problem of production of a deposit in the microreactor is solved by ultrasonic treatment. However, there is a strong possibility that irregular turbulent flow and cavitation generated in a microchannel by ultrasound do not always successfully act on a target reaction. Scaling up has been coped with a method of increasing the number of microreactors, that is numbering up, but the number of microreactors which can be stuck is limited to several dozen, thus inherently aiming exclusively at products of high value, and the increase in the number of devices leads to an increase the absolute number of failure causes, and when the problem of clogging actually occurs, it can be very difficult to detect a problem site such as failure site.
In view of the above problems, it is an object of the present invention to provide a reaction method of an organic compound and a production method of an organic compound which comprise performing a reaction of an organic compound in a forced thin film fluid formed between processing surfaces arranged to be opposite to each other so as to be able to approach to and separate from each other, at least one of which rotates relative to the other. This makes it possible to achieve high reaction selectivity according to the purpose and a high production rate of a target substance because the temperature of the thin film fluid is highly uniform and high uniformity in a reactor is achieved by stirring. Further, it is also possible to control the molecular weight distribution of a reaction product and a selective reaction irrespective of whether a target organic reaction is a reaction which produces a deposit or a reaction which produces no deposit because clogging of a reaction product does not occur due to self-dischargeability and high pressure is not required. Further, it is also possible to secure reaction uniformity irrespective of whether the viscosity of a fluid is low or high because a reaction is performed in a forced thin film fluid and therefore the viscosity of a fluid has a low impact on reaction uniformity, and to achieve a high productivity, and to achieve scale-up production while minimizing risks specific to organic reactions because a reaction is performed in a thin film fluid.